Lasersaber developed a DC to DC converter that drives a regular incandescent, CFL, LED and halogen bulb and runs off 12V. He calls it Joule Ringer V. 3.0.
In his video he tries out CFL, LED, halogen and incandescent light bulbs all with reasonably bright light. He powers it with a small 12V battery pack, I’m guessing NiCd, since it has to furnish a lot of current. But he tries it with a single AA cell and gets a dimly lit filament. You can see in the frozen video frame that it’s quite bright, which is surprising for a high wattage incandescent. He doesn’t say anything about how hot the 2N3055 gets, but it has no heatsink at all, which means that it must be getting warm. One advantage he pointed out is that the circuit shuts off when the bulb is removed. That means that the on/off switch for the lamp can serve as the on/off switch for the circuit.
The simplicity of the circuit is amazing, just a coil, transistor and light. And a battery, of course. This may be its Achilles heel, since there is nothing to limit the current. I don’t see a problem with putting an amp of current through the base to emitter junction in the forward direction, as long as it doesn’t exceed that too much. But the light might have a reverse current, and in this case it’s well over a hundred volts if the light is bright, If the incandescent light shorts, which it often does when in a regular lamp, then the emitter to base junction will be melted and the transistor will be dead. CFLs sometimes go bad; I’ve seen them with the transistors and chips blown apart from excessive current. If this happens in this circuit, it’s most likely the same thing will occur.
I think it I had it, I would put two 1N4003 diodes in series and then across the emitter to base, with the cathodes pointing towards the base. It might be a good idea to put another pair across these, only in the other direction. Then if the E-B or B-E voltage becomes excessive, the diodes will conduct and shunt the damaging current away from the junction.
But in all cases, this circuit is putting over a hundred volts across a 2N3055, which has a maximum voltage rating of 60V, and was never meant to handle anything higher than maybe 70 or 80 volts. There’s no neon light, no zener, no anything to protect the transistor from overvoltage. Why people don’t choose an appropriate high voltage transistor is a mystery to me. They’re free in all those old PC power supplies that people often have laying around. And they come with a free heatsink, too, and they’re already mounted on it. It’s so easy to just unsolder one or both and use them instead of burning out a whole bunch of 2N3055s.
I have boxes of 2N3055s, maybe I should try to make one of these to see how it works. But I won’t pay $30.00 for a ferrite bar. I may use one of those Big Old Toroids I got from BG Micro. At least the price is right.
I said DC to DC converter because the current going through the light also goes through the base to emitter junction of the transistor. This acts like a diode, through which current is supposed to go one way only. If the voltage gets excessive and the current goes through both ways, then the transistor is going to be damaged.
Back to experimenting…